fix: bounds check in GateSeparatorPolynomial for virtual sumcheck rounds#22130
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fix: bounds check in GateSeparatorPolynomial for virtual sumcheck rounds#22130
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GateSeparatorPolynomial::current_element() and univariate_eval() accessed betas[current_element_idx] without bounds checking. During virtual sumcheck rounds (when current_element_idx >= betas.size()), this read out-of-bounds memory, causing non-deterministic debug assertion failures. The fix returns FF(1) when current_element_idx is past the betas array, which is mathematically correct: virtual rounds have no additional beta challenges, so the gate separator factor is trivially 1.
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This was referenced Mar 30, 2026
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Summary
Fixes non-deterministic debug build assertion failure in
SumcheckTests/0.Prover:GateSeparatorPolynomial::current_element()andunivariate_eval()accessedbetas[current_element_idx]without bounds checking. During virtual sumcheck rounds (whencurrent_element_idx >= betas.size()), this read out-of-bounds heap memory. The fix returnsFF(1)when past the betas array, which is mathematically correct since virtual rounds have no additional beta challenges.Full analysis: https://gist.github.com/AztecBot/909e3998f506b0dd6d07a211841dbeb8
ClaudeBox log: https://claudebox.work/s/4028b7cc57fc1903?run=1